Image enlarging cathode-ray tube



June 1944. K. KOHL 2,350,774

IMAGE ENLARGING CATHODE RAY TUBE Filed NOV. 26, 1940 i Fi )NVENTOR ,Kar'l Kohl ATTORNEY Patented June 6, 1944 IMAGE ENLARGING CATHODE-RAY TUBE Karl Kohl, Berlin, Germany; vested in the Alien Property Custodian Application November 26, 1940, Serial No. 367,194 In Germany October 31, 1939 Claims.

It is known to make, electric occurrences visible by letting an electron current of a Braun tube strike a luminous screen and by subjecting the ray itself, while it passes through the tube, to a deflection or intensity control. Thes methods are of importance principally in television in which the Braun tube has proved to be a particularly suitable reproducing means. However, the control of the electron ray requires a certain amplitude of the control voltage or makes it necessary to amplify control voltages if they are too small. In some cases, for example in ultra high frequency occurrences, suitable amplifiers are not known so that, hitherto, it has practically not been Possible to form more exact ideas of the oscillation occurrences in ultra high frequency oscillations.

The invention provides means for solving the problem mentioned above. It relates to a device for enlarging the image produced by the oscillogram of a Braun tube. The invention consists in making Visible the magnified oscillogram produced by the cathode ray of the Braun tube by means of an electron microscope or amplified by a relay. Preferably, the oscillogram is produced by the cathode ray of the Braun tube on an intermediate screen with additional secondary emission. The intermediate screen may be constructed as a fine grid or as a foil of such thinness that the striking electron ray releases a corresponding secondary emission at the back of the intermediate screen. However, the electrodes, particularly those of the electron microscope system, may be arranged at the side so that the secondary emission issued at the front of the intermediate screen is received by the electron microscope arrangement. Before reaching the intermediate screen, the electron current may, if necessary by omitting the screen, be subjected to an intensity or deflection control. Instead of a receiving screen, a corresponding electrode or a system of electrodes may be provided, whose received current intensity is used for releasing relay or amplifier actions.

The invention is illustrated by way of examples in the accompanying drawing in which:

Fig. 1 shows a cathode I of usual construction, for example in the shape of a cylinder, in which the axis coincides with the axis of the emitted ray. 2 is a concentration cylinder. In the tube there are arranged electrodes 3, 4, 5, to which suitable electric potentials are applied and which cause the electron ray to be projected through corresponding openings in these electrodes upon the screen 6. 3 is a control electrode to which is applied the potential to be examined. 0f course, instead of one electrode, several electrodes may be provided for the control. 1 represents a thin foil or a grid made of a substance emitting secondary electrons when being hit by an electron ray. These secondary electrons, naturally, travel in the direction of the maximum potential and are, therefore, drawn to the right, since the electrode 4 on the right, as indicated, has the maximum potential But, owing to the high velocity imparted to the electrons, they fly through the electrode 4 as well as through the electrode 5, which has a somewhat lower potential than the electrode 4, and finally they hit the screen 6 mentioned above. Now, the electrodes 4 and 5 act like a system of electron microscope lenses as, owing to their presence, the ray 8 formed by the secondary electrons will, similar to a light ray passing through a glass lens, produce on the screen ii an enlarged image of the original place of the secondary electron ray. of course, the foil 1 must be very thin so that the secondary electrons are emitted sufiiciently concentrated on the side facing the screen 6.

Fig. 2 shows a modification in which the surface 1 of the screen 6 is arranged so that the secondary electrons released at the front of the surface I will be received by the electron microscope 4, 5 and will appear on the screen 6 as an enlarged image.

On the other hand, an electron microscope arrangement may be provided between the control electrode or control electrodes 3 and the surface I. If desired, the surface 7 may be replaced by the receiving screen 6. With the means described above, it is possible to make electric occurrences sufiiciently visible even with the smallest control amplitudes and independent of the wave length or frequency employed. As this is connected with an amplification, the arrangement may be used as a regular amplifier or relay arrangement. In the last mentioned cases it is, for example, possible to use a regular electrode instead of the screen 6 or, if necessary, a system of several electrodes whose currents are influenced by the increased defiection or intensity control. Therefore, the new arrangement may be employed not only in television and the like, but may also serve any other purposes of amplification and releasing of relays.

What is claimed, is:

1. A device for enlarging the image produced by the oscillogram of a Braun tube, comprising a receiving screen, an intermediate screen in the shape of thin foil, means for forming an electron ray and causing the same to hit the screen and thereby. release from the back an emission of secondary electrons and means for focusing said secondary electrons on said screen to produce an image of the oscillogram.

2. A device for enlarging the image produced by the oscillogram of a Braun tube, comprising a receiving=;screen,-an intermediate screen at an angle to said-receiving screen and being provided with a layer adapted to emit secondary electrons,

and two or more electrodes forming an electron; H

microscope disposed at right angles to said receiving screen, the potentials of said electrodes diminishingtoward said receiving screen, thesecondary emission issued atthe frontof said irid termediate screen being enlarged by said electron microscope upon said receiving screen.

3. A device for enlarging the image-produced by the oscillogram of a Braun tube, comprising a receiving screen, an intermediate screen at an angletosaid receiving screem and being provided "With-a layer adapted to emit secondary-electrons, "twoor more electrodes-forming an electron micro-- --scope 'disposed at right angles'to said receiving screen, the potentials of said electrodes diminishing toward said receiving screen, the secondary emission issued at the front of said intermediate screen being enlarged by said electron microscope upon said receiving screen, and means for controlling the intensity and deflection of electron rays before reaching said intermediate screen.

4. In acathode ray tube of the character described, means for producing. a ray of primary electrons moving in a controlled manner alongrar predetermined path, ,an intermediate electrode I positioned across said pathtobe impacted by the primary electrons andadapted to emit secondary electrons morenumerous than the primary elec-' trons impacting it, an electron microscope positioned adjaceht'said intermediate electrode to concentrate the secondary electrons in a stream along a predetermined path, and a receiving screen extending across the path of said secondary electrons. I

5. Apparatus as described in claim l wherein said receiving screen is a luminous screen and wherein the ray of primary electrons'is deflected by scanning means. i 

